Networked sound masking system

ABSTRACT

A sound masking system for shaping the ambient noise level in a physical environment. The sound masking system comprises a networked and distributed system having a number of master units coupled together and to a control unit. One or more of the master units may include satellite sound masking units which function to reproduce the sound masking signal generated by the master sound masking unit. Each of the master units is addressable over the network by the control unit enabling the control unit to program the contour, spectral band, and gain characteristics of the sound masking output signal. The system may also include a remote control unit which provides the capability to tune and adjust each master sound masking unit in situ without requiring physical access through the ceiling installation.

CROSS-REFERENCE TO RELATED APPLICATIONS

This invention is a continuation of U.S. patent application Ser. No.“15/060,433,” filed on Mar. 3, 2016, entitled “Networked Sound MaskingSystem,” which is a continuation of U.S. patent application Ser. No.13/890,824, filed on May 9, 2013, entitled “Networked Sound MaskingSystem,” which is a continuation of U.S. Pat. No. 8,477,958, filed onFeb. 26, 2001, also entitled “Networked Sound Masking System.” Theentire content of each of the foregoing patent applications isincorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to sound masking, and more particularly toa networked and remote controllable sound masking system.

BACKGROUND OF THE INVENTION

Sound masking systems are widely used in offices and similar workplaceswhere an insufficient level of background sound results in diminishedspeech privacy. Such environments suffer from a high level of noisedistractions, and lower comfort levels from an acoustic perspective.Sound masking systems operate on the principle of masking which involvesgenerating a background sound in a given area. The background sound hasthe effect of limiting the ability to hear two sounds of similar soundpressure level and frequency simultaneously. By generating anddistributing the background noise in the given area, the sound maskingsystem masks or covers the propagation of other sounds in the area andthereby increases speech privacy, reduces the intrusion of unwantednoise, and improves the general acoustic comfort level in the area orspace.

Sound masking systems are of two main types: centrally deployed systemsand independent self-contained systems. In a centrally deployed system,a central noise generating source supplies a series of loudspeakersinstalled throughout the physical area or space to be covered. Theindependent self-contained system comprises a number of individualself-contained sound masking units which are installed in the physicalspace. The sound masking units operate independently of each other, butmay include a number of satellite speakers which extend the range ofeach self-contained, i.e. master, sound masking unit. Most sound maskingsystems include the capability for broadcast announcements and musicover the loudspeakers contained in the sound masking units.

The primary goal of sound masking systems is to provide an unobtrusive,effective masking sound that is adjustable for maximum consistency, andoffers the ability to meet the requirements of the occupants. Themasking output is preferably sufficient to accommodate the existingacoustic requirements of the workplace environment and adjustable tohandle changes to the acoustic characteristics of environment whichoccur over time. Similar demands are placed on the system for the publicaddress and music functions. In short, the preferred sound maskingsystem would produce an output with a frequency and volume level that iscontrollable to produce the desired acoustic response for workplacezones ranging in size from the smallest to larger spaces.

Centralized systems are characterized by achieving uniformity of output,but not uniformity of acoustic response for the space. In a centralizedsystem, the frequency spectrum of the sound masking output can only beadjusted at a centrally located equalizer, and as a result the soundmasking output has the same frequency spectrum for all of theloudspeakers. Depending on the configuration of the centralized system,volume adjustments may be made for very large physical spaces, i.e.zones, by adjusting the amplifier output; for relatively smaller zones,volume adjustments are made by changing wiring connections or controlson the speaker enclosure, or by adjusting a hardwired zone volumecontrol. In practice, it is difficult to accommodate environmentalacoustic variations using a centralized system because the volume andfrequency spectrum adjustments required for the typical physical zonesize are too large to achieve a uniform acoustic result. A furtherdisadvantage is that many of the adjustments for a centralized soundmasking system require an installer or technician to re-enter theceiling space or to rewire the speakers in the system.

The independent self-contained system has a number of importantadvantages over the centralized arrangement. The independentself-contained system is more effective in terms of sound generation,volume adjustment, and frequency adjustment which, in turn, improves theperformance of such systems as compared to centralized systems. Inparticular, the independent self-contained system provides a definednon-frequency specific output range for the masking output spectrum, andadjustments can be made at each master sound masking unit. The volumecontrols for an independent self-contained system also provide moreflexibility than in the centralized system, and provide for fineradjustments in smaller zones, in addition to centralized volume controlsfor large zone or global adjustment. However, with existing systems itis still necessary to re-enter the ceiling to adjust the frequencyspectrum and volume output level for each master sound masking unit, andthe controls for providing multi-unit volume zone adjustments requirethe hardwiring of the units.

While existing independent self-contained systems are more flexible thancentralized systems in many regards, they do not satisfy all therequirements of an ideal sound masking system as discussed above.Furthermore, other shortcomings are associated with existing soundmasking systems. In both centralized and independent self-containedsystems, the public address and music volume controls are limited in thesame manner as described above for sound masking output volume controls.Second, any centrally located controls only affect the output level forthe speakers or sound masking units which have a hardwired connection.It will be appreciated that this severely limits the adjustability ofthe system to future changes in the acoustic environment unless at leastsome of the system is rewired. Third, the tuning procedure for existingsystems is time consuming and can still be inaccurate over the systemeven when undertaken with the appropriate level of skill and attention.And fourthly, adjustments to existing systems must be made on-site.

Accordingly, there remains a need for a networked sound masking systemwith individually controllable and programmable sound masking units, andwhich system is easily adaptable to changing sound qualities in aphysical space or spaces in a building environment.

BRIEF SUMMARY OF THE INVENTION

The present invention provides a networked sound masking system withindividually controllable and programmable sound masking units.

In a first aspect, the present invention provides a sound masking systemfor controlling the ambient noise level in a physical environment, thesound masking system comprises: (a) a communication network spanning atleast a portion of the physical environment; (b) a plurality of soundmasking units, some of the sound masking units include a sound maskingcomponent for generating a sound masking output signal and some of thesound masking units include a communication interface for coupling thesound masking units to the communication network for receiving controlsignals over the communication network; (c) a control unit having acommunication interface for coupling to the communication network fortransmitting control signals over the communication network to the soundmasking units, and the control signals include signals for controllingthe operation of at least some of the sound masking units.

In another aspect, the present invention provides a sound masking systemfor shaping the ambient noise level in a physical environment, the soundmasking system comprises: (a) a communication network spanning at leasta portion of the physical environment; (b) a plurality of sound maskingunits, some of the sound masking units include a sound masking circuitfor generating a sound masking output signal for shaping the ambientnoise level in the vicinity of each of the sound masking units, aprogrammable controller and at least one digital component forcontrolling operation of the sound masking circuit, and a communicationinterface for coupling the sound masking units to the communicationnetwork, and the programmable controller being coupled to thecommunication network for receiving control signals from thecommunication network for altering the operation of the sound maskingcircuit; (c) a control unit, the control unit having a communicationinterface for coupling the control unit to the communication network fortransmitting control signals over the communication network to the soundmasking units, and the control signals include signals for controllingthe operation of at least some of the sound masking units; (d) whereinthe sound masking circuit comprises a random noise generating componentfor generating an incoherent signal output, a filter component forreceiving the incoherent signal output and generating an incoherentsignal output with a predetermined contour, and an output amplifier foramplifying the contoured incoherent signal output, and the digitalcomponent comprising a digital potentiometer coupled to the filtercomponent for altering the contour of the incoherent signal output inresponse to control signals from the programmable controller.

In a further aspect, the present invention provides in a networked soundmasking system for controlling ambient noise level in a physicalenvironment, the networked sound masking system having a communicationnetwork for coupling a plurality of sound masking units, the soundmasking units span the physical environment, the sound masking unitsinclude a sound masking component for generating a sound masking outputsignal and include a communication interface to the communicationnetwork for receiving control signals over the communication network,and a control unit having a communication interface for coupling thecontrol unit to the communication network for transmitting controlsignals to the sound masking units, and the control signals includesignals for selectively controlling the operation of the sound maskingunits, a remote control unit for generating adjustment signals for thecontrol unit for adjusting characteristics of the sound masking signaloutput produced by the sound masking units, the remote control unitcomprises: (a) a remote communication interface for transmitting theadjustment signals to the control unit, and the control unit has anexternal communication interface compatible with the remotecommunication interface; (b) an input component for receiving soundlevel readings for the physical environment; (c) a component responsiveto the sound level readings for generating the adjustment signalsassociated with the characteristics of the sound masking output signalfor the sound masking units.

Other aspects and features of the present invention will become apparentto those ordinarily skilled in the art upon review of the followingdescription of specific embodiments of the invention in conjunction withthe accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

Reference will now be made to the accompanying drawings, which show, byway of example, a preferred embodiment of the present invention, and inwhich:

FIG. 1 shows in block diagram form a networked sound masking systemaccording to the present invention;

FIG. 2 shows a sound masking unit in block diagram form for thenetworked sound masking system of FIG. 1;

FIG. 3 shows in block diagram form a control unit for the networkedsound masking system of FIG. 1;

FIG. 4 shows the control unit of FIG. 3 in more detail, and inparticular the functional modules for the control unit;

FIG. 5 shows in flowchart form a main functional processing method forthe control unit of FIG. 3;

FIG. 6 shows in flowchart form the processing steps for thedisplay/setup function in the control unit for the networked soundmasking system according to the present invention;

FIG. 7 shows in flowchart form the processing steps for the timerfunction in the control unit for the networked sound masking system;

FIG. 8 shows in flowchart form the processing steps for thegain/contour/paging/band setting functions in the control unit for thenetworked sound masking system;

FIG. 9 shows in flowchart form the processing steps for the equalizerfunction in the control unit for the networked sound masking system;

FIG. 10 shows in flowchart form the steps for setting the timer functionfor the control unit;

FIG. 11 shows in flowchart form the processing steps for a diagnosticsfunction in the control unit for the networked sound masking system;

FIG. 12(a) shows in flowchart form the steps for a system configurationfunction in the control unit for the networked sound masking system;

FIG. 12(b) shows in flowchart form the steps for configuring addressesfor the sound masking units according to an aspect of the presentinvention;

FIG. 13 shows in flowchart form the processing steps for the timerfunction for the control unit;

FIG. 14 shows in flowchart form functions for controlling the soundmasking units in the networked sound masking system according to thepresent invention;

FIG. 15 shows in flowchart form functions implemented for the remotecontrol unit in the networked sound masking system according to thepresent invention;

FIG. 16 shows in flowchart form the processing steps for an equalizationfunction in the networked sound masking system according to the presentinvention; and

FIG. 17 shows in graphical form a Prescribed Spectrum Contour table forthe LD sound masking signal.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Reference is first made to FIG. 1, which shows in block diagram form anetworked sound masking system according to the present invention andindicated by reference 10.

As shown in FIG. 1, the networked sound masking system 10 comprises acontrol unit 12, and a network 13 comprising a plurality of master soundmasking units 14, indicated individually by 14 a, 14 b, 14 c, . . . 14n, and one or more satellite sound masking units 16, indicatedindividually by 16 a, 16 b, 16 c, 16 d, . . . 16 m. The physicalconnections for the network 13 between the master sound masking units 14may comprise 5, 4 or 3 conductors. In a 5 conductor arrangement, twoconductors carry power, two conductors provide a communication channel,and one conductor provides for paging.

The master sound masking unit 14 and the satellite sound masking units16 provide the sound masking functionality, i.e. sound masking andsignal generation and amplification. Each sound masking group, i.e.master sound masking unit 14 together with the associated satellitesound masking units 16, is configured for a particular physical spaces,e.g. office, room, zone in a open office, etc. The master sound maskingunits 14 are configured to generate a specific sound masking signal at aspecified output level for performing the sound masking in the physicalspace. As will be described in more detail below, the sound maskingsignal is generated according to programmable spectrum, equalizer, andvolume settings. The satellite sound masking units 16 are connected totheir associated master unit 14 and comprise a speaker which reproducesthe sound masking signal generated by the master unit 14. The satelliteunits 16 provide a cost-effective way to expand the coverage of themaster sound masking unit 14 in a building space.

The control unit 12 as will be described in more detail couples to thenetwork 13 and provides the capability to adjust the functional aspectsof the master sound masking units 14 and the satellite sound maskingunits 16. The sound masking functions include masking signal spectrum,masking signal output volume, and paging volume. The control unit 12also provides diagnostic functions and timer control functions. Thecontrol unit 12 may also include testing functions, such as a testfunction which compares existing sound measurements to the desired soundparameters for the space and calculates the adjustments to be made.

The control unit 12 configures the network 13 by assigning identities oraddresses to each of the master units 14. The addressing of theindividual master units 14 enables the control unit 12 to directcommands and/or status requests to individual master sound masking units14 (and the associated satellite sound masking units 16), or to groupsof master sound masking units 14, or to the entire network 13 as awhole. The control unit 12 is then used to set/adjust the masking signalspectrum, the masking signal volume, and/or the paging volume for theselected (i.e. addressed) master and satellite sound masking units 14and 16. According to another aspect, the master sound LD masking units14 may include a digital equalizer for providing greater programmingflexibility over the spectrum for the sound masking signal generated bythe selected master and satellite sound masking units 14 and 16.

As also shown in FIG. 1, the system 10 may include a remote control unit18. The remote control unit 18 works in conjunction with the controlunit 12 to display and/or change the current adjustment settings (i.e.spectrum adjustment settings, equalizer settings, masking signal volumelevel, and paging volume) for the master units 14. As described below,the remote control unit 18 can accept as input sound measurements takenby a sound level meter, or another configuration the remote control unit14 allows a user to measurements of the acoustical environment for thebuilding space. The remote control unit 18 communicates with the controlunit 12 through a communication interface 20, for example a radio signalchannel, indicated by reference 19.

In addition to the communication channel 19 for the remote control 18,the control unit 12 may also include another communication interface 58.The communication interface 58 provides the capability to access thecontrol unit 12 via a remote location, e.g. an offsite location. Thecommunication interface 58 may comprise a telephone communication, radiocommunication, computer network (e.g. a Local Area Network (LAN) or aWide Area Network (WAN)), or a connection through the Internet or WorldWide Web (WWW). This provides greater flexibility in configuring,adjusting and maintaining the sound masking system 10 from a remote oroff-site location.

Reference is next made to FIG. 2 which shows the master sound maskingunit 14 in greater detail. As shown in FIG. 2(a), the master unit 14comprises a random noise generator stage 30, a filter stage 32, anequalizer stage 34, and an audio power amplifier stage 36. The operationof the stages 30, 32, 34, 36 is controlled by a microcontroller 38. Asalso shown, the master sound masking unit 14 includes a communicationinterface 40. The communication interface 40 couples the master unit 14to the network 13 and provides the capability to communicate with thecontrol unit 12 and other master sound masking units 14 b, 14 c in thenetwork 13. The master unit 14 includes a local power supply 42 forpowering the circuitry. The audio power amplifier stage 36 drives aspeaker 44 which emits the sound masking signal.

The random noise generator stage 30 is the signal source for generatingthe sound masking signal. The random noise generator 30 may comprise amulti-stage shift register and an Exclusive-OR gate network as describedin U.S. Pat. No. 4,914,706 which issued to the assignee in common withthe subject application. Alternatively, the random noise generatormodule 30 may be implemented in firmware executed in the microcontroller38. The random noise generator 30 may also be implemented as anoperational amplifier which couples and amplifies the noise produced bya voltage regulator circuit, such as a Zener diode.

The filter stage 32 is coupled to the output of the random noisegenerator 30. The filter stage 32 comprises two filters connected to therespective outputs of the last two stages of the shift register (notshown) in the random noise generator 30 as described in U.S. Pat. No.4,914,706. Each of the filters comprises a resistive-capacitive laddernetwork, with one of the filters having a higher cut-off frequency thanthe other filter. Using this arrangement, each of the filters derives adifferent output signal from the random noise generator 30 with each ofthe output signals having a different spectral shape within the definedaudio frequency range.

In the preferred embodiment, the filter stage 32 is coupled to themicrocontroller 38 through a digital control device 33. The digitalcontrol device 33 comprises a potential divider which is connectedbetween the output ends of the filters in the filter stage and under thecontrol of the microcontroller 38 the output contour of the filter stage32 is programmable. The digital control device 33 is preferablyimplemented using a digital potentiometer, such as the device availablefrom XICOR Corp., and has a continuously adjustable tap with at least 32tap positions. The tap positions are selectable by the microcontroller38, and by changing the tap positions the spectral shape of the noisesignal output from the random noise generator 30 is controllable.

The equalizer stage 34 comprises an one-third Octave equalizer which isused for adjusting the sound spectrum of the noise signal output to thedesired contour. In the preferred embodiment, the equalizer comprises 18adjustable bandpass filter cells for the 1/3 Octave band and 7adjustable bandpass filter cells for the 1/1 Octave band, and an adderfor summing the outputs. Each filter cell is implemented using anoperational amplifier or OP Amp, fixed resistors and capacitors as willbe within understanding of one skilled in the art. Preferably, each ofthe filter cells is coupled to the microcontroller 38 through a digitalcontrol device 35, such as a digital potentiometer to provide for theindependent adjustment of the cell about a fixed center frequency underthe control of the microcontroller 38. In the present embodiment, the1/3 Octave Band frequencies comprise 160, 200, 250, 315, 400, 500, 630,800, 1000, 1250, 1600, 2000, 2500, 3150, 4000, 5000, 6300 and 8000 Hertz(Hz). The 1/1 Octave Band frequencies comprise 125, 250, 500, 1000,2000, 4000, and 8000 Hz. Each filter cell is preset to the prescribedcontour, e.g. 48 dB<V.sub.f1<57 dB and 24 step<DigiPot.sub.1<30 step.The output from the equalizer stage 34 is a sound masking signal with acontrollable contour which is fed to the amplifier power stage 36.

The audio power stage 36 provides a controllable output level for thecontoured sound masking signal. The contoured sound masked signal isamplified by the audio power stage 36 and output to the speaker 44 whichemits a sound masking sound into the physical space. The audio powerstage 36 also provides an adjustable amplification level for theproviding paging announcements, background music or other broadcastsover the speaker. In the preferred embodiment, the output level of theaudio power stage 36 is also controllable by the microcontroller 38through a digital control device 37. Preferably, the digital controldevice 37 comprises a digital potentiometer having at least 32 stepsettings.

Referring still to FIG. 2, the communication interface 40 comprises afirst serial interface 46, a second serial interface 48, and a switchinglogic stage 50. The communication interface 40 couples themicrocontroller 38 to the network 13 and allows the unit 14 to receiveand transmit status requests and control commands. The switching logicstage 50 connects the microcontroller 38 to the first and second serialinterfaces 46 and 48. The first serial interface 46 allows themicrocontroller 38 to communicate with an upstream device, for example,the master sound masking unit 14 a or the control unit 12. The secondserial interface 48 allows the microcontroller 38 to communicate with adownstream device, for example, the master sound masking unit 14 c. Inconjunction with the switching logic stage 50, the microcontroller 38monitors the serially encoded messages and acts upon messages which areaddressed to the specified master sound masking unit 14. Each of themaster sound masking units 14 is assigned an address according to aself-addressing mechanism as will be described in more detail below.

The satellite sound masking units 16 are associated with respectivemaster sound masking units 14. The satellite sound masking units 16 eachinclude a speaker, and are coupled to one of the master sound maskingunits 14. The satellite sound masking units 16 act as slaves orsatellites to the master sound masking unit 14 and reproduce the soundmasking signal output generated by the associated master sound maskingunit 14.

Reference is next made to FIG. 3, which shows the control unit 12 inmore detail. As shown, the control unit 12 comprises a processor unit(i.e. a microprocessor) 42, a program memory 44, a data memory 46, adisplay module 48, a keypad 50, a real-time clock module 52, a parametermemory 54, a serial communication interface 56, and the communicationinterface 58. As shown in FIG. 4, the control unit 12 includes afunctional module 60 to control the 1/3 Octave equalizer 34 (FIG. 2(a)),a functional module 62 to provide volume control, a functional module 64to provide paging volume control, a functional module 66 to providespectrum adjustment control of the contoured sound masking signal, afunctional module 68 to provide timer functions for the system 10, afunctional module 70 to provide addressing of the master sound maskingunits 14 in the network 13, and a functional module 72 for performingdiagnostic functions. The operation of the functional modules in thecontrol unit 12 is now described in more detail with reference to theflowcharts in FIGS. 5 to 17.

Reference is first made to FIG. 5, which shows a start-up process 100for the control unit 12. The start-up process 100 is executed inresponse to a power-up 101 or a reset condition. The start-up process100 comprises an initialization step 102 which includes configuring thecontrol unit 12. After the initialization step 102, the control unit 12runs a display/setup operation 104 as a background loop, and a timeroperation LD 106. The timer operation 106 is periodically executed, forexample, on an interrupt driven basis or as part of a polling loop inthe display/setup operation.

Reference is next made to FIG. 6, which shows the display/setupoperation 104 in more detail. As shown the display/setup operation 104comprises displaying a series of menu functions on the display 48(FIG. 1) which are accessed via selections from the keypad 50 (FIG. 1).As shown in FIG. 6, the menu functions include a Date/Time function menu110, a Gain function menu 112, a Contour menu function 114, a PagingVolume function menu 116, an Equalizer Setting function menu 118, aTimer function menu function 120, a Diagnostic function menu 122, aSystem Configuration function menu 124, and Serial Number function menu126.

The processing steps for the Date/Time function menu 110 are shown inFIG. 7. The first step comprises displaying the time 130 and promptingthe user to change the time 132. If the user selects to change the time,then a set time procedure 134 is executed. Otherwise the date isdisplayed 136, and the user is prompted to change the date 138. If theuser selects to change the date, a set date procedure 140 is executed.

Reference is next made to FIG. 8, which shows in more detail theprocessing steps for setting the Gain function 112, the Contour Controlfunction 114, the Paging Volume function 116, and the Equalizer Bandfunction 118. The steps for controlling each of these functions isimplemented according to the process 111 shown in FIG. 8. As shown, thefirst step comprises selecting the master sound masking unit. Indecision block 150, a selection is made between a single master soundmasking unit 14 or multiple master sound masking units 14. If multiplemaster sound masking units 14 are to be configured, then the next step154 involves selecting the range for the sound masking units 14. Thesound masking level, i.e. the gain, for the sound masking units 14 inthe range is entered in block 156 and transmitted via the network 13 toall the sound masking units 14 in the selected range. After the soundmasking level has been sent to the sound masking units 14 in the range,the first sound masking unit 14 a in the range is selected, i.e.addressed.

Referring still to FIG. 8, the next step 162 involves reading the soundmasking gain level setting for the master sound masking unit 14 whichwas selected in step 160 or as a result of the branch from decisionblock 152. The gain level setting received from the sound masking unit14 is compared to the desired setting stored in the control unit 12, andif a change in the sound masking level is needed as determined indecision block 164, then the desired sound masking gain level setting issent to the selected master sound masking unit 14 in block 166. If nochange is indicated for the selected master sound masking unit 14, thenthe next master sound masking unit 14 in the network 13 is selected,i.e. addressed, and the steps 162 and 164 are repeated. The sameprocessing steps are utilized for setting the Contour Control function114, the Paging Volume function 116, and the Equalizer Band function118.

Reference is next made to FIG. 9, which shows in more detail theprocessing steps for the operation of the Octave equalizer module 60 forthe control unit 12. The first step 170 comprises prompting the user toselect the desired equalizer band. As described above, the 1/3 OctaveBand frequencies comprise 160, 200, 250, 315, 400, 500, 630, 800, 1000,1250, 1600, 2000, 2500, 3150, 4000, 5000, 6300 and 8000 Hertz (Hz); andthe 1/1 Octave Band frequencies comprise 125, 250, 500, 1000, 2000,4000, and 8000 Hz. Next in block 172, the band menu for the selectedband is displayed, and the user is prompted to enter the setting for theband. The control unit 12 then prompts the user to select the nextequalizer band in block 174.

Reference is next made to FIG. 10, which shows the operation of thetimer functional module 68 and menu in more detail. The first step 180as shown in FIG. 8 comprises prompting the user to select one of themaster sound masking units 14 for setting the timer function. Inresponse to the user's action, the control unit 12 displays theWeekday/Time/Level setting for the selected unit 14, and the user isprompted to change the setting. If the user changes the setting in step184, then the new setting is stored by the control unit 12 and alsoapplied to the selected sound masking unit 14.

Reference is next made to FIG. 11, which shows the operation of thediagnostic functional module 68 and menu for the control unit 12 in moredetail. The first step 190 involves prompting the user to select one ofthe master sound masking units 14 for the diagnostic test. In response,the control unit 12 retrieves the serial number from the master soundmasking unit 14 over the network 13 as indicated by block 192. If thereis an error (as indicated by decision block 194), then a communicationerror 196 is logged for that unit 14 and another unit 14 is selected210. If there is no communication error (decision block 194), then thecontrol unit 12 checks the serial number against the entry stored in alookup table in block 198. If the serial number does not match the entryin the lookup table, then an identification error is logged in block202, and another master sound masking unit 14 is selected in block 210.If the serial number matches the entry in the lookup table (decisionblock 200), then the status for the master sound masking unit 14 isqueried by the control unit 12 in block 204. The status of the selectedmaster sound masking unit 14 is checked in block 206, and if the statusis fail or does not meet specifications, then a status error is loggedin block 208. The next step in block 210 involves selecting anothermaster sound masking unit 14 and repeating steps 192 through 210, asdescribed above, until all, or the selected group, of the master soundmasking units 14 have been queried as determined in block 212. The laststep in the operation of the diagnostic function module 68 comprisesgenerating and/or displaying a diagnostics report as indicated in block214.

Reference is next made to FIG. 12(a), which shows the operation of thesystem configuration and addressing functional module 70 and menu forthe control unit 12 in more detail. The control unit 12 is preferablypassword protected, and the first step 220 involves prompting the userto enter a password. If the password is incorrect (decision block 222),then further access is denied (block 224). If the entered password iscorrect, the password is displayed in block 226, and the user is giventhe option of changing the password (decision block 228). If the userchanges the password, then the new password is saved in block 230. Thenext step 232 involves displaying the number of master sound masking 14that are presently configured for the network 13. If the system 10 isbeing setup for the first time, the number of units may be configured atthe factory or entered in the field by the technician. The user is giventhe option of changing the number of units 14 configured for the system10 in decision block 234, and the new number of units 14 is stored instep 236.

Referring still to FIG. 12(a), in decision block 238, the user isprompted to initialize the system 10. If the user elects to initializethe system 10, then the control unit 12 executes an initializationprocedure indicated generally by reference 240. The initializationprocedure 240 is shown in more detail in FIG. 12(b). As shown, the firststep 241 in the initialization procedure 240 involves resetting all ofthe master sound masking units 14 connected to the network 13. As aresult of the reset operation 241, each of the master sound maskingunits 14 has a logical address of 0. Since all of the units 14 havelogical address 0, the first sound masking unit 14, i.e. unit 14 a,responds when the control unit 12 queries the units 14 as indicated byblock 242. The selected unit 14 is then queried for its serial number inblock 244. The serial number 244 is assigned to the unit 14 at the timeof manufacture and preferably comprises a code stored in non-volatilememory in the unit 14. The serial number may be rewritten by the controlunit 12 as described in more detail below. The control unit 12 uses theserial number to generate a unit address, i.e. logical address, for theunit 14 as indicated in block 246. The serial number is preferablystored in memory, for example a look-up table in the control unit 12,and provides a cross-reference to the master sound masking unit 14. Thecurrent logical address generated in step 246 is unique for the unit 14in the present network configuration 10, but for another networkconfiguration the logical addresses may be regenerated. Following theaddressing operation, the next sound masking unit 14 is selected by thecontrol unit 12 and the current logical address is incremented for thenext sound masking unit 14. The operations for assigning the currentlogical address to the unit 14 based on the serial number according tosteps 244 to 248 are repeated. These operations are repeated until allof the sound masking units 14 have been assigned current logicaladdresses by the control unit 12 as indicated by decision block 250.Following this scheme, the current logical address for the last soundmasking unit 14 is equal to the number of sound masking units 14connected to the networked system 10.

Reference is next made to FIG. 13, which shows the timer function 106(FIG. 5) in more detail. In response to an interrupt or a request from apolling loop, a wake-up call or “clock tick” is periodically issued asindicated in step 260, and a schedule of timed events is checked inblock 262. The timed events may comprise, for example, changes in thelevel of the sound masking signal for all or some the master soundmasking units 14 (and the associated satellite sound masking units 16).If the schedule indicates that there is no change in sound maskinglevel, then the timer function 106 goes to sleep (block 266). If thereis a scheduled change, then the new level for the sound masking signalis transmitted via the network 13 to the affected sound masking units 14(block 268).

Reference is next made to FIG. 14, which shows in flowchart form thecontrol structure 300 for controlling the master sound masking units 14.As shown, the control structure 300 includes an initialization procedure301, a program serial number procedure 302, a read serial numberprocedure 303, an assign logical address procedure 304, a read soundmasking signal level procedure 305, and a write sound masking signallevel procedure 306.

The initialization procedure 301 comprises a function 304 for resettingthe logical addresses and a function 306 for generating and writinglogical addresses for the units 14 as described above with reference toFIG. 12. The program serial number procedure 302 provides a mechanismfor programming or regenerating the serial number stored in non-volatilememory for each unit 14. The procedure 302 comprises a write serialnumber function 312. The read serial number procedure 303 comprises aread serial number function 314 which the control unit 14 utilizes toread the serial numbers of the units 14, for example, as described abovewith reference to FIG. 12. The assign logical address procedure 304comprises a write address function 316 for writing, i.e. assigning,logical addresses to the sound masking units 14. The read levelprocedure 305 comprises a read level function 318 which allows thecontrol unit 12 to read the current level setting for the sound maskingsignal in the unit 14 being addressed by the control unit 14 or theremote control unit. The write level procedure 306 comprises a writelevel function 320 which allows the control unit 12 (or remote controlunit) to write, i.e. set, the level setting for the sound masking signalin the unit 14 being addressed by the control unit 14 or the remotecontrol unit. Once the unit 14 is selected, the control unit 12 nextselects the function to be queried/programmed, and then reads theparameter setting from the digital control device 33 to 37 (e.g. thedigi-pot for the filter stage 32 in FIG. 2) using the read levelfunction 318, or writes the parameter setting to the digital controldevice 33 to 37 (e.g. the digi-pot the audio power amplifier stage 36 inFIG. 2), using the write level function 320.

As described above with reference to FIG. 1, the remote control unit 18works in conjunction with the control unit 12 to display and/or adjustthe current adjustment settings (i.e. spectrum adjustment settings,equalizer settings, masking signal volume level, and paging volume) forthe master units 14. The remote control unit 18 is operated through menufunctions as shown in FIG. 15. Referring to FIG. 15, the function menusfor the remote control unit 18 comprise a gain control menu 350, acontour control menu 352, a paging control menu 354, and an equalizercontrol menu 356. The user uses these menus to program (i.e. write) andread the gain, contour, and paging functions as described above for thecontrol unit 12.

As described above, the sound masking units 14 according to the presentinvention include an equalizer stage 34 which allows the shaping of thesound spectrum of the sound masking noise signal output. Advantageously,the capability to address each of the sound masking units 14 allows theequalizer stage 34 to be individually set for each of the units 14 or agroup of the units 14, and this capability greatly enhances thefunctionality of the networked sound masking system 10 according to thepresent invention.

Reference is made to FIG. 16 which shows a procedure 400 according toanother aspect of the invention for controlling the equalizer functionin each of the sound masking units 14. According to this aspect, theremote control unit 18 (FIG. 1) includes a serial communicationinterface 21 (e.g. radio or hard-wire link) which couples to a soundlevel meter 23 (FIG. 1), such as the RION NA-27 meter. The sound levelmeter 23 is used to take sound level readings for the physical space andthese readings are transmitted to the remote control unit 18 via theserial communication interface 21. As will now be described withreference to FIG. 16, the readings from the sound level meter 23 areused in conjunction with settings in a Prescribed Contour Table storedin the control unit 12 or the remote control unit 18 to adjust the levelsettings in the equalizer stages 34 for the sound masking units 14.

As shown in FIG. 16, the first operation in the equalization procedure400 comprises selecting a 1/1 Octave analysis or a 1/3 Octave analysisas indicated in block 402. The next operation involves selecting betweenan automatic mode of operation or a manual mode of operation asindicated in block 404. Once the mode of operation is selected, the user(i.e. technician) enters the unit ID to address the sound masking unit14 on which the equalizer function is to be adjusted/programmed (block406). Once the unit 14 is addressed, the remote unit 18 queries the unit14 for the first sound level setting L.sub.o for the first frequencyband f.sub.o as indicated in block 408.

Referring still to FIG. 16, if the automatic mode of operation isselected (block 404), then the sound level meter 23 reads the levelsetting L from the unit 14 (block 410) and the level setting L iscompared to a minimum level setting L.sub.min in block 412 and a maximumlevel setting L.sub.max in block 414. The minimum L.sub.min and maximumL.sub.max level settings are determined from a Prescribed Contour Table500 (block 416) such as depicted in FIG. 17. If the level setting L isnot greater than the minimum level setting L.sub.min, then the remoteunit 18 sends a command or message to the control unit 12 to increasethe level setting L for the equalizer by one step, as indicated in block418. If the level setting L is greater than the minimum level settingL.sub.min, then the level setting L is compared to the maximum levelsetting L.sub.max in decision block 414. If the level setting L is notless than the maximum level setting L.sub.max, then the remote unit 18transmits a message to the control unit 12 to decrease the level settingL for the equalizer by one step as indicated in block 420. The controlunit 12 makes the adjustment to the equalizer setting for the addressedunit 14, and sends a confirmation message to the remote unit 18. Theremote unit 18 then accepts a new reading from the sound level meter 23and the remote unit 18 reads the level setting L in block 410 and thesteps in blocks 412, 418, 420 are repeated until the level setting L isset within the desired range L.sub.min to L.sub.max as defined by thePrescribed Contour Table 500 (FIG. 17). For example, the PrescribedContour Table 500 includes the following level ranges (L.sub.min,L.sub.max) for the center frequencies in the 1/1 Octave band or 1/3Octave band:

TABLE-US-00001 (L.sub.min, L.sub.max) Center Frequency 48 dB, 56 dBF.sub.0=160 Hz 47.5 dB, 54.5 dB F.sub.1=250 Hz . . . 6.5 dB, 23 dBF.sub.17=8000 Hz

Referring back to FIG. 16, once the level setting L for the currentfrequency band is set within the range L.sub.min to L.sub.max, the levelsetting L for the next frequency band is selected as in block 422, andthe remote control unit 18 sends a signal to the sound level meter 23 toread the next level setting L (block 410).

In the manual mode of operation (as selected in block 404), the firstoperation LD involves using the remote control unit 18 to receive anddisplay a level setting L from the sound level meter 23 as indicated inblock 424. In block 426, the level setting L is compared to the rangeL.sub.min to L.sub.max. If the level setting L is not within theprescribed range, the desired level setting L is set or adjusted usingthe remote control unit 18 as indicated in block 428. In block 430, theremote control unit 18 is used to select the next frequency band forreading the next level setting (block 424).

As described above, the remote control unit 18 in conjunction with asound level meter 23 provides an effective mechanism for adjusting theequalizer function in each of the sound masking units 14 through thecontrol unit 12 and networked connection without the need for openingthe ceiling tile to physically access any of the units 14.

The present invention may be embodied in other specific forms withoutdeparting from the spirit or essential characteristics thereof. Certainadaptations and modifications of the invention will be obvious to thoseskilled in the art. Therefore, the presently discussed embodiments areconsidered to be illustrative and not restrictive, the scope of theinvention being indicated by the appended claims rather than theforegoing description, and all changes which come within the meaning andrange of equivalency of the claims are therefore intended to be embracedtherein

What is claimed is:
 1. A sound masking system for controlling theambient noise level in a physical environment, said sound masking systemcomprising: (a) a communication network spanning at least a portion ofsaid physical environment; (b) a plurality of sound masking units, someof said sound masking units including a sound masking component forgenerating a sound masking output signal and said sound masking unitsincluding a communication interface for coupling said sound maskingunits to said communication network for receiving control signals oversaid communication network; (c) a control unit, said control unit havinga communication interface for coupling said control unit to saidcommunication network for transmitting control signals over saidcommunication network to said sound masking units, and said controlsignals including signals for selectively controlling the operation ofsaid sound masking units.